This project examines the role of emerging gastrointestinal pathogens in Peru, a developing country. Newer viral agents appear to be important causes of childhood diarrhea. Cyclospora cayetanensis, a coccidial parasite recently identified by our group, is an important cause of disease in children, travelers and AIDS patients. Cysticercosis is an important cause of late onset epilepsy and other neurological conditions. The epidemiology or viral diarrhea in our shanty town population will be defined using recently developed diagnostic tools for detection of new viral agents including astro, enteric adeno, calci, norwalk and toro viruses. The importance of secondary rotavirus infection will be determined. Cyclospora cayetanensis, is a protozoa recently identified by our group and named after the Peruvian university, Cayetano Heredia. Its epidemiological role in children's diarrhea, and its seroprevalence will be described in a Peruvian shanty town. The antigenic and molecular structure of Cyclospora cayetanensis will be further defined. Children infected with this parasite will be randomized for treatment in a double blind trial to determine if trimethoprim/sulfamethoxazole is an effective therapy. New immunological tools for diagnosing cysticercosis will be developed and then tested in Peru, a highly endemic zone. Pigs, an intermediate host of cysticercosis, will be used as sentinels to predict changes in environmental infection with Taenia solium eggs.